Technological map for the repair of a synchronous motor. Technological map of repair of windings of an asynchronous motor

04.03.2020

Loosen the bolts securing the outer bearing caps and remove them. If there are snap rings between the bearing cover and the bearing, they must be removed and stored. Loosen the bolts securing the shield to the frame. Remove cover, seal and terminal board. Remove the front bearing shield from the sharpening of the frame using the forcing bolts or a lever inserted into the gap between the end of the frame and the edge of the shield.

Rice. 1.1. Removing the back cover

Spin evenly until the shield is completely out of the centering sharpening, while it is necessary to support the shaft, preventing the rotor from hitting the stator. Remove the endshield from the shaft by turning it without distortion on the bearing. Remove the rotor from the stator special device (rice. 2.4), without touching the stator and the stator winding. Remove the rear shield in the same way as the front. Using a universal puller or on a stand, remove the bearings from the rotor shaft by the inner race. Remove inner covers. Attach order number tags to stator, rotor and endshields. Place disassembled parts on racks for subsequent operations.

Rice. 1.2 Removing the back cover

When disassembling parts associated with tension (coupling halves, pulleys, etc.), they sometimes resort to heating them with autogenous burners No. 5 or by the induction method. The shaft on which the part is mounted is wrapped with a wet asbestos cloth or asbestos. Heating with burners starts from the outer edges of the part and gradually moves to the seating surfaces. The puller must be under tension. The beginning of the descent of the part is controlled by a click and loosening of the tension of the puller. Sometimes solid carbon dioxide is used to cool the shaft. The heating temperature is controlled by thermoelectric thermometers or resistance thermometers. It is not recommended to control the heating by touching the part of the tin bar.

Rice. 1.3 Removing the front cover

When removing ball bearings from the rotor shaft induction motors the following requirements must be met:

it is not allowed to remove ball bearings by the outer ring, the force should be applied only to the inner ring of the bearing; if it is impossible to remove the bearing by the inner ring, the bearing removed by the outer ring is rejected;
it is not allowed to use a hammer, chisels or drifts to remove bearings;
it is forbidden to strike the cage, balls and other parts of the ball bearing

Fig.2.1 Extraction of the rotor from the stator

Dismantled ball bearings are placed in a special container and sent for washing in a washing machine at a temperature detergent composition 80-90 °C. It is possible to clean bearings in a bath using an ultrasonic unit. If after washing the bearings are not used immediately, they should be preserved with AC spindle oil. If long-term storage is required, the bearings are coated with a protective lubricant, for which they are immersed in a bath with technical vaseline heated to 70 ºС. The bearings are lowered into the bath with a hook, without touching them with your hands. After cooling, the bearings are wrapped in paraffin paper.

Fig.3.1 Troubleshooting bearings front and rear covers

Fig.3.2 Visual inspection of the stator winding

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3.11 Technological map of the current repair of asynchronous electric motors 6kV PEN.

	Name of operations	NTD (drawings, etc.)	Control operations					Note
	Name of operations	NTD (drawings, etc.)		Criteria				Note
3.11.1 Disassembly of the electric motor.
	Remove the stator terminal cover, disconnect the power cable and wires of resistance thermometers, disconnect the ground	OVK.412.106 TO		Clean surface of terminals, Integrity of insulators and threads of studs, tight fit of lugs on cables	hot-smoked 12x13 sandpaper, gasoline, soldering iron	Oxidation of the terminal surfaces, cracking of insulators, stripping of the threads on the studs, violation of the fastening of the lugs on the cables	Grind the surface of the leads, rinse with gasoline, replace the insulators if necessary, solder the tips
	Disconnect and remove diffusers from ED.	OVK.412.106 TO
	Remove air filter, blow through and dry	OVK.412.106 TO			Device for blowing, gasoline B-70, hot-smoked 10x12
3.11.2 Revision of the stator.
	Check fastening (from the outside) of the stator ventilation struts	OVK.412.106 TO	OK tapping with a hammer	Homogeneous, dull sound and no rattling	Hammer 0.2 kg	Loose fastening	Weld defective spacers
	Remove dust, dirt, oil and inspect the frontal parts of the stator winding	OVK.412.106 TO		Contaminant-free, tightly wrapped bands and spacers seated		Loose bandages and struts	Re-bandage the end windings, install spacers
3.11.3 Assembly of the electric motor.
	Install diffusers on the ED.	OVK.412.106 TO
	Install the air filter.	OVK.412.106 TO
	Connect the power cable, wires of resistance thermometers, connect grounding, close the cover of the stator terminals,	OVK.412.106 TO					Clean the surface of the terminals, rinse with gasoline, replace the insulators if necessary, solder the tips

After assembly, make a control measurement of the motor insulation resistance and absorption coefficient with a 2500V megohmmeter. The insulation resistance must be at least 40 MΩ, the absorption coefficient must be at least the value specified in clause 1.3.2.

3.12 Technological map of the current repair of asynchronous electric motors 6 kV TsN.

	Name of operations	NTD (drawings, etc.)	Control operations		Fixtures, tools, equipment	Possible defects, malfunctions		Note
	Name of operations	NTD (drawings, etc.)		Criteria	Fixtures, tools, equipment	Possible defects, malfunctions		Note
3.12.1 Disassembly of the electric motor.
	Remove the stator terminal cover, disconnect the power cable and wires of resistance thermometers, disconnect the ground			Clean surface of terminals, Integrity of insulators and threads of studs, tight fit of lugs on cables	hot-smoked, sandpaper, gasoline, soldering iron	Oxidation of the terminal surfaces, cracking of insulators, stripping of the threads on the studs, violation of the fastening of the lugs on the cables	Grind the surface of the leads, rinse with gasoline, replace the insulators if necessary, solder the tips
	Measure the air gap between stator and rotor				Probe set		Make a decision to transfer the engine to the KR to set the required air gap.
3.12.2 Revision of the stator.
	Clean and blow out ventilation ducts, bores, end windings, stator housing with compressed air				Blower, lint-free cloth
				Contaminant-free, tightly wrapped bands and spacers seated	Bandage needle, bandage tape		Re-bandage the end windings, install spacers
3.12.3 Assembly of the electric motor.
	Measure the air gap between stator and rotor			Compliance of clearances with requirements (Table 4.1).	Probe set	Air gap inconsistency with the required values	Make a decision to transfer the engine to the KR to set the required air gap.
	Connect the power cable, wires of resistance thermometers, connect grounding, close the cover of the stator terminals,			Clean surface of terminals, Integrity of insulators and threads of studs, tight fit of lugs on cables	hot-smoked, sandpaper, gasoline, soldering iron	Oxidation of the terminal surfaces, cracking of insulators, stripping of the threads on the studs, violation of the fastening of the lugs on the cables	Clean the surface of the terminals, rinse with gasoline, replace the insulators if necessary, solder the tips

a) clean the oil gauges from external contaminants;

b) unscrew the damping bolt from the oil indicator, clean the internal cavity of the damping chamber of the oil indicator and the damping bolt from contamination; install a new sealing head gasket of the stilling bolt and screw the bolt back. It is allowed, if necessary, to lubricate the sealing gasket of the head of the stilling bolt with a thin layer of oil-resistant sealant KLT-75;

c) check the absence of plaque on the internal surfaces of the glass, which makes it difficult to visually control the oil level, mechanical damage in the form of cracks and chips; clean the “breathing” hole in the upper cover of the oil indicator with a soft wire;

d) blow out the oil gauges with compressed air with a pressure of no more than 2 kg/cm 2 to check the patency of the oil gauge with control by the air pressure coming out through the "breathing" hole;

If traces of oil leaks are found through the seals of the oil indicator, plaque on inner surface glass, which makes it difficult to visually check the oil level, foreign particles (sealant residues, etc.) or other defects, the oil gauge is completely disassembled and the defects are eliminated with subsequent assembly. In this case, the resting bolt is screwed into place last, after the sealant that seals the glass has hardened. After assembly, the oil indicator is installed on the oil tank with the inspection hole of the small indicator housing in the direction opposite to the motor housing, after which the oil indicator is re-checked according to item d).

When installing the floorboards of the upper part of the body and the connecting jumpers between the floorboards, use sealant (paint) in the threaded connection of the jumpers as a countermeasure.

3.13 Routing current repair asynchronous electric motors 6 kV (NR).

	Name of operations	NTD (drawings, etc.)	Control operations		Fixtures, tools, equipment	Possible defects, malfunctions		Note
	Name of operations	NTD (drawings, etc.)		Criteria	Fixtures, tools, equipment	Possible defects, malfunctions		Note
3.13.1 Dismantling the electric motor.
	Remove the stator terminal cover, disconnect the power cable, ground	IAEG.528122.002 TO		Clean surface of terminals, Integrity of insulators and threads of studs, tight fit of lugs on cables		Oxidation of the terminal surfaces, cracking of insulators, stripping of the threads on the studs, violation of the fastening of the lugs on the cables	Grind the surface of the leads, rinse with gasoline, replace the insulators if necessary, solder the tips
	Remove shroud and cooler fan	IAEG.528122.002 TO			hot-smoked 14x17, center punch, sledgehammer 3kg, mounting crowbar
	Remove the outer covers (flanges) of the bearings	IAEG.528122.002 TO
3.13.2 Revision of the stator.
	Remove dust, dirt, oil and inspect the frontal parts of the stator winding	IAEG.528122.002 TO		Contaminant-free, tightly wrapped bands and spacers seated	Bandage needle, bandage tape	Loose bandages and struts	Re-bandage the end windings, install spacers
3.13.3 Inspection of bearings.
	Remove old grease	IAEG.528122.002 TO			Bath for washing parts, gasoline B-70
	Inspect bearing	IAEG.528122.002 TO		No visible defects		Dimples, spalling, wear marks, matt tracks on rolling surfaces, deformation of balls or rollers	Replace bearing	If replacement is necessary, issue a Defect Report
3.13.4 Cooler revision.
	Clean and blow out cooler tubes with dry air	IAEG.528122.002 TO			Blower, lint-free cloth, cleaning rod
3.13.5 Assembly of the electric motor.
	Install both shields on the electric motor	IAEG.528122.002 TO			Crane beam, supports, dynamometric hot-smoked 17x19, center punch, sledgehammer 3kg.
	Install outer bearing caps	IAEG.528122.002 TO
	Install the cooler fan and shroud.	IAEG.528122.002 TO
	Connect power cable, ground. Close the cover of the stator terminal box,	IAEG.528122.002 TO		Clean surface of terminals, integrity of insulators and stud threads, tight fit of lugs on cables	hot-painted 14x17, sandpaper, gasoline, soldering iron	Oxidation of the terminal surfaces, cracking of insulators, stripping of the threads on the studs, violation of the fastening of the lugs on the cables	Clean the surface of the terminals, rinse with gasoline, replace the insulators if necessary, solder the tips

3.14 Technological map of the current repair of the backup exciter DAZ-18-10-6 (U3), GSP-2000-1000.

	Name of operations	NTD (drawings, etc.)	Control operations		Fixtures, tools, equipment	Possible defects, malfunctions		Note
	Name of operations	NTD (drawings, etc.)		Criteria	Fixtures, tools, equipment	Possible defects, malfunctions		Note
3.14.1 Exciter disassembly.
	Remove cable covers and disconnect power cables			clean surface	hot-rolled 17x19, glass paper	Lead oxidation	Sand the surface of the leads, rinse with gasoline
	Disconnect bearing temperature sensor cables	6BS. 345.030.036		clean surface	hot-rolled 17x19, glass paper	Lead oxidation	Sand the surface of the leads, rinse with gasoline
	Disconnect the cables from the alternator control panel	1BS. 217.038.039		clean surface	hot-rolled 17x19, glass paper	Lead oxidation	Sand the surface of the leads, rinse with gasoline
3.14.2 Inspection of the generator stator.
	Inspect the stator output			Clean surface of the tips, No rips or cracks in the insulation	Glass paper, fiberglass, electrical tape	Tip oxidation, insulation damage	Grinding, tinning of tips, isolation of conclusions
	Tighten screw connections		VK, test tightening	Tight tightening of threaded connections	Kit wrenches	Loosening of threaded connections	Tighten loose screw connections
3.14.3 Assembling the exciter.
	Connect the cables to the generator board	1BS. 217.038.039		clean surface	hot-smoked set, glass paper	Lead oxidation
	Connect bearing temperature sensor cables	6BS. 345.030.036		clean surface	hot-smoked set, glass paper	Lead oxidation	Clean the terminal surfaces, rinse with gasoline
	Install cable covers and connect power cables			clean surface	hot-smoked set, glass paper	Lead oxidation	Clean the terminal surfaces, rinse with gasoline

When replacing a bearing, it must be pressed off the shaft using a screw puller. The new bearing is washed from conservation grease in B-70 gasoline. Heat the bearing in an oil bath or with an inductor to a temperature of 90°C and press onto the shaft. Refer to Appendix 20 for bearing mounting recommendations. Shaft fit is tight. Then the bearing is filled with grease (LITOL-24, SVEM, TsIATIM-201). After assembly, make a control measurement of the motor insulation resistance and absorption coefficient with a 2500V megohmmeter. The insulation resistance must be at least 40 MΩ, the absorption coefficient must be at least the value specified in clause 1.3.2.

The scheme of the technological process for the repair of asynchronous motors and synchronous generators is shown in Figure 69 and does not require special explanations.
Since this manual is intended for students of electrification faculties of agricultural universities, future electrical engineers, the manual describes the most important, according to the authors, issues of repairing electrical machines. In addition, it should be taken into account that the All-Union State All-Union Order of the Red Banner of Labor Research Institute for the Repair and Operation of the Machine and Tractor Park (GOSNITI) has developed technological maps and manuals for overhaul asynchronous electric motors, welding and automotive electrical equipment.

Scheme of the technological process of repair of squirrel-cage electric motors.
These documents are compiled in the form of tables that list the numbers and contents of all technological operations, specifications and instructions for carrying out repairs, provides information about the equipment, fixtures and tools needed for repairs. Technological maps are supplemented with diagrams, sections, drawings. In the repair industry, various technical documentation is compiled, it is not the same at different plants and in individual departments, although the content of individual documents is close, and some of them are duplicated even at the same plants. Thus, Glavelectroremont of the METI recommends that its enterprises fill out a defective note and a list of defects after the fault detection of machines.
The content of the note includes the passport data of the machine before repair and the customer's wishes for changing them. It contains all the dimensions of the stator and rotor cores and the winding data of the stator and rotor (winding type, number of slots, wire brand, number of turns in the coil, number of parallel conductors in a turn, number of coils in a group, phase, winding pitch, number of parallel branches, phase conjugation, wire consumption in kilograms, head extension, heat resistance class).
Everything is recorded in the list of defects necessary operations throughout the machine, for example, the frame - weld cracks, repair locking surfaces, weld legs, repair fasteners and eye bolt, etc.
Each repaired machine is accompanied by a technological card, which contains information about the customer, technical specifications machine with its passport data, the value of the phase resistance, the cross section of the output ends and the insulation class, the size of the stator core and the number of slots, information about the winding data before repair and by calculation, information about the mechanical part - its condition, information about winding control and bench tests.
The technological map is signed by a troubleshooting technician, a foreman, a calculation engineer and QCD employees.
The drying officer fills in the drying logs of electrical machines, which include: the customer, order number, passport data of the machine, drying place, information about the beginning of drying, the temperature of individual elements of the machine, the insulation resistance of the stator and rotor windings and the end of drying. The final results are certified by the person responsible for the drying and the head of the site.
Separately, the Quality Control Department maintains a book of test reports for each repaired machine. OTK. also draws up an act on the transfer of successfully tested machines to the warehouse finished products. The act indicates the repair number of the machine, type, power, insulation class, voltage, speed, form of execution, price list, repair cost, customer. The act is signed by the head of the QCD and the head of the warehouse.
Approximately the same form is drawn up an act of issuance of finished products indicating the total amount of repair costs. The act is signed by the management of the repair enterprise and the representative of the customer.
Technical documentation for the repair of transformers is more extensive in general and in terms of the content of individual documents. For example, the content of a troubleshooting note includes not only passport data, data of the HV and LV windings and the dimensions of the magnetic circuit, but also the mass of oil, the removable part and the total mass of the transformer.
The note is signed by the persons who wound the windings and assembled the transformer, and the master.
Separately, a protocol for the analysis of transformer oil is filled out, in which the customer, the place, reason and date of sampling, the duration of the oil operation and the results of physical, chemical and electrical analyzes of the oil are indicated. Give a conclusion about the quality of the oil. The protocol is signed by the person who conducted the analysis, the site engineer.
For each transformer, a repair (revision) form is filled out containing the following information: about the customer, transformer passport, work and measurements performed during the repair process for all components and parts of the transformer (tank, radiator, expander, exhaust pipe, tank and expander fittings, transport fixtures, HV, MV and LV bushings, valve and bushing flange cover seals, magnetic circuit and its grounding, HV, MV, LV windings and the state of their pressing, voltage switch, winding insulation details, taps and circuit, oil, additional data), o drying (drying method, its beginning and end, temperature during drying, inspection and crimping after drying, DC winding resistance in phases of all windings at the measurement temperature), preliminary tests (determination of transformation ratios for all windings and taps, insulation resistance, checking the electrical strength of the insulation), on the final tests (data from the experiments of idling and short circuit , transformation ratio test, resistance of all windings in phases at measured temperature, winding group, winding capacitance ratios at different frequencies, etc., insulation test with applied voltage, turn insulation test, oil strength). At the same time, data on the devices used in the tests are entered into the form. The form is signed by the person who conducted the tests, the QCD foreman, the workshop foreman and Chief Engineer.
The transformer drying logs and the protocol for the analysis and testing of transformer oil are attached to the form.
For repaired transformers, certificates of acceptance of finished works are drawn up. In the process of repair, they draw up a limit card-report on the consumption of materials, on the basis of which the cost of repairing transformers is determined. Defection of electrical equipment. Fault detection methods
Fault detection is the definition of machine malfunctions during operation or repair. There are two stages - fault detection of the assembled machine and after its disassembly.
Fault detection of a machine or apparatus is one of the most critical operations, since undetected malfunctions can lead to the destruction of the machine in operation, an accident, and an increase in the duration and cost of work during repeated repairs.
Electrical equipment is characterized by the presence of two parts - electrical and mechanical. When fault-finding the mechanical part of electrical equipment, they check the condition of the fasteners, make sure that there are no cracks in one or another part, determine wear and tear and compare it with permissible standards, measure air gaps and compare with tabular values, etc.
All detected deviations from the norms are recorded and entered in the list of defects or a repair card, the forms of which are different at different plants, but the content is almost the same.
Malfunctions in the electrical part of a machine or apparatus are hidden from the eyes of a person, so they are more difficult to detect. The number of possible faults in the electrical part is limited to three:
open circuit;
the short circuit of individual circuits between themselves or the circuit of the circuit (circuits) on the body;
the closure between a part of the turns of the winding (the so-called inter-turn or turn closure).
These faults can be identified using the following four methods:
test lamp or resistance method (ohmmeter);
method of symmetry of currents or voltages;
millivoltmeter method;
electromagnet method.
Consider the definition of faults in the assembled machine or apparatus.
An open in a winding without parallel circuits can be determined by using a test lamp. If there are two or more parallel branches in the winding, a break is determined with an ohmmeter or an ammeter and a voltmeter. The obtained value of the winding resistance (for example, the armature winding of a DC machine) is compared with its calculated or passport value, after which a conclusion is made about the integrity of the individual branches of the winding. Breaks in multi-phase machines and devices that do not have parallel branches can be determined by the current or voltage symmetry method, but this method is more complicated than the previous one.
It is somewhat more difficult to determine a break in the rods of squirrel-cage rotors of asynchronous electric motors. In this case, resort to the method of current symmetry.
Experience in determining breaks in rods is as follows. The rotor of the electric motor is slowed down and a voltage reduced by 5 ... 6 times compared to the rated voltage is supplied to the Stator. An ammeter is included in each of the phases of the stator winding. With good stator and rotor windings, the readings of all three ammeters are the same and do not depend on the position of the rotor. When the rods break in the rotor, the readings of the instruments are different, most often
two ammeters show the same currents, and the third one shows a smaller current. When the rotor is slowly rotated by hand, the readings of the instruments change, the reduced current value will follow the rotation of the rotor and goes from one phase to another, then to the third, etc.
This is explained by the fact that when the rotor turns, the damaged rods move from the zone of one phase to the zone of another. inhibited asynchronous electric motor similar to a transformer in short circuit mode. Breakage of the rod is equivalent to transferring the damage zone from the short circuit mode to the load mode, which leads to a decrease in the current in the stator winding in that part of it that interacts with the damaged rod.
If several rotor rods break, the readings of all ammeters may be different, but, as mentioned above, they will cyclically change and follow one after the other (passing through the phases of the stator winding) with slow rotation of the rotor. Different readings of ammeters, independent of the rotation of the rotor, indicate damage or defects in the stator winding, but not the rotor.
The location of the break in the windings of the rotors of squirrel-cage motors is determined using an electromagnet. The rotor, mounted on an electromagnet, is covered with a sheet of paper, on which steel filings are poured. When the electromagnet is turned on, the sawdust is located along the entire rods and is absent in the break zone.
Breaks in the armature windings of DC machines are determined using an ohmmeter (millivoltmeter).
The closure of individual electrical circuits of electrical equipment to the housing or to each other is determined using a test lamp. Often in this case, megohmmeters are used. The latter should be given preference, since they are easy to determine the circuit with a relatively high resistance at the point of contact between the circuits or with the case.
The short circuit between the sections lying in different layers of the grooves of the section armatures on the body is determined using an ohmmeter (millivoltmeter).
The coil circuit in multi-phase electrical machines and devices is determined by the method of symmetry of such and voltages or by special devices, for example, the EJI-1 type.
So, turn short circuits in the windings of three-phase electric motors are determined at idle their operation using the current symmetry method (the readings of all three ammeters included in each phase of the stator winding should be the same in the absence of turn short circuits), and turn short circuits in the stator windings of synchronous generators are determined at idle using the voltage symmetry method (the readings of all three voltmeters connected to the stator winding terminals must be the same).
When determining turn short circuits in the windings of three-phase transformers, both the current and voltage symmetry method is used.

Rice. 7. Scheme for determining turn short circuits in equipment coils.
Turn short circuits in the windings of single-phase electrical machines and transformers are determined with an ohmmeter or ammeter. When determining turn short circuits in the excitation coils of DC machines, it is advisable to use low-voltage alternating current rather than direct current to increase the sensitivity of the test by selecting the appropriate instruments (ammeter and voltmeter).
It should be noted that the turn short circuit in the windings of electrical equipment operating on alternating current is accompanied by a sharp increase in current in the damaged winding, which, in turn, leads to a very rapid heating of the winding to unacceptable limits, the winding starts to smoke, char and burns.
The place of turn circuits in the stator windings of AC electrical machines is determined using an electromagnet. The place of turn short circuits in the armature windings of DC machines is determined with an ohmmeter (millivoltmeter).
Usually damaged coils of transformers are not defective, but if necessary, the electromagnet method can be used (Fig. 7).
The fault detection of DC and AC machines and transformers during repair is described in detail in the workshop on installation, operation and repair of electrical equipment.

Dismantling of electrical machines. Removing the old winding

Dismantling electrical machines into their component parts is not difficult. It is only necessary to mechanize the performance of individual operations as much as possible, using electric or hydraulic wrenches, pullers, hoists, etc., and also be careful when removing the rotors of large machines so as not to damage the stator iron packages or its winding with the rotor.
The most time-consuming operation during disassembly is the removal of the old winding. This is done by the following methods: mechanical, thermomechanical, thermochemical, chemical and electromagnetic.
Essence mechanical method is that the body electrical machine with stator steel packages and winding are installed on a lathe or milling machine and cutter or
one of the frontal parts of the winding is cut with a cutter. Then, with the help of an electric or hydraulic drive, the remaining part of the winding is removed (pulled out) from the grooves (with a hook for the remaining frontal part of it). However, with such a removal of the winding, there are remains of insulation in the grooves, and additional costs are required for their removal.
2. With the thermomechanical method of removing the old winding, an electric machine with a cut off end of the winding is placed in a kiln at a temperature of 300 ... 350 ° C and kept there for several hours. After that, the rest of the winding is easily removed. Often the machine is placed in a furnace with the entire winding (none of the ends of the winding is cut off), but in this case, after firing, the winding is removed from the grooves only manually.
It is difficult to create a uniform thermal field in a kiln. Quite often, the winding insulation ignites in the furnace, leading to a sharp increase in temperature in the furnace, especially in some of its zones. When the temperature rises above the permissible level, machine bodies can warp, especially aluminum cases. Therefore, machines with aluminum bodies are not recommended to be fired. Some enterprises investigate the distribution of temperatures inside the furnace during its operation and determine the zones in which it is possible to locate electrical machines with aluminum casings.
During firing in a furnace, stator steel sheets are annealed, specific losses in steel are noticeably reduced and efficiency increases; cars. However, the lacquer films between the steel package and the housing and between the individual steel sheets burn out. The latter leads to the fact that after 2 ... 3 firings the tight fit between the package and the body is broken, the package begins to rotate in the machine body, and the package pressing is weakened. Therefore, the firing of the insulation of the windings of machines in molten salts (caustic or alkali) can be considered progressive.
Roasting in molten salts is carried out at a temperature of 300°C (573K) with aluminum cases and 480°C (753 K) with cast iron for several minutes. The complete absence of air access to the firing object, as well as the ability to control the temperature within the required limits, make it possible to use this firing method for machines with aluminum casings. Warping of the latter is completely excluded.
With the thermochemical method of winding removal, an electric machine prepared for firing (one of the frontal parts of the winding is cut off) is lowered into a container with a solution of caustic soda or alkali. The machine is in solution at a temperature of 80...100°C for 8...10 hours, after which its winding can be easily removed from the grooves of the stator packs. With this method, no warping of the hulls can occur. This method is especially justified for oil-bitumen insulation of windings.
In the chemical method, an electrical machine with a winding is placed in a container with washing liquid of the MF-70 type. This liquid is volatile and toxic, therefore, when working with it, safety regulations must be observed. The technology for removing the windings is as follows: loading the container with repaired machines, sealing the container, filling it with liquid, the reaction process, which usually takes night time off, removing the liquid, purging the container freed from liquid with clean air, depressurizing and opening the container, removing electrical machines and removal of the winding from the stator slots.

5. The electromagnetic method is as follows. A single-phase transformer is made with a removable armature and one removable, more precisely, replaceable core. A magnetizing winding is wound on an irreplaceable rod for mains voltage. One or more motor stators are put on the second removable rod, the winding insulation of which must be burned. The diameter of the replaced rod is selected in such a way as to obtain the smallest (about 5 mm) gap between the stator bore and the rod. The method is convenient in that it is possible to regulate the heating temperature of the stator by changing the voltage supplied to the magnetizing winding or switching the number of its turns. With this method, machines with both cast iron and aluminum bodies can be fired.

By design windings of electrical machines are divided into three types: concentric, loose and template. The latter, in turn, are subdivided into windings with continuous compounded insulation and sleeve. They are used in large machines with a voltage of 3.6 kV and higher, so they are not considered in this book.
In practice, the repair of windings consists in removing the old one and making a new winding, which has the same or improved data of slot insulation and winding wire.
Concentric winding is the most obsolete, laborious and is used only in electrical machines with closed slots. The manufacture of this winding consists of the following basic operations: the manufacture of slotted insulating sleeves using templates, the material for which is selected depending on the voltage of the machine and its heat resistance class; laying sleeves in grooves; filling the sleeves with metal or wooden studs according to the dimensions of the insulated winding wire; the choice of a winding scheme, in which the smallest voltages are obtained between adjacent conductors in the groove of the machine; preparing the wire for winding coils, which consists in removing the insulation at the ends of the wire prepared for winding the coil and waxing it to facilitate pulling it through the grooves; winding with two winders of the smallest coil using special templates for forming the frontal parts of the coil; winding the remaining coils, their connection and isolation.
In the manufacture of bulk windings, insulating slot boxes are first prepared and placed in the grooves. In this case, it should be borne in mind that in machines of the old series, the slot boxes consist of two layers of electric cardboard and one layer of varnished cloth. They were replaced by slotted boxes, consisting of film-electrocardboard, and at present, in small machines of new series, only one thin layer of insulating film is used. Under these conditions, the use of new materials, including winding wires, when repairing old-series electric machines significantly increases their reliability and, if necessary, can be accompanied by a noticeable increase in machine power. On the contrary, when repairing machines of new series, it is necessary to use only appropriate high-quality materials and winding wires, otherwise the repair of the machine will lead to a decrease in its reliability, deterioration in technical and economic indicators and a sharp decrease in its power. In addition, it is necessary to take into account the narrow specialization and mechanization of work at electrical engineering plants and more. low level technologies of work at repair enterprises, which also affects the quality of work, the fill factor of the machine slot and its reliability. The next winding operation is winding on special, size-adjustable coil templates. This is followed by the laying of coils in grooves, the installation of wedges, which can also be used in low-power machines of new series, as well as a film, connecting and bundling the winding with insulating cords or stockings with the installation of insulating interphase spacers on the frontal parts of the winding. If it is necessary to connect individual coils, they are isolated with linoxin, PVC or glass-lacquer tubes.
Connections between the coils can be made either by soldering (the ends to be joined are tinned, twisted and dipped in a bath of molten solder), or by resistance welding using manual tongs with a graphite electrode.
Drying of the windings of electrical machines, before and after impregnation, is carried out in drying ovens (convective method), losses in stator or rotor steel (induction method), losses in windings (current method) and infrared irradiation (radiation method).
Usually, electrical repair enterprises have vacuum or atmospheric drying ovens, the volume of which is determined at the rate of 0.02 ... 0.04 m 3 /kW of the power of the machines for which the oven is intended. The heater can be electric, including lamp, steam or gas. The heater power is determined at the rate of approximately 5 kW per 1 m 3 of the furnace volume. Rational air circulation must be ensured in the oven. Thus, the drying power is greater, the greater the number and power of the machines being dried. Drying time ranges from several hours (6...8) for small machines to several tens of hours (70...100) for large machines.
Drying machines by induction requires a magnetizing winding. This method is useful for drying large machines that are best dried at installation or repair sites rather than in a drying oven. This method is more economical than the previous one both in terms of power consumption and drying time.
Drying with current is even more beneficial. The duration of drying is reduced in comparison with drying in ovens by 5...6 times, and power consumption - by 4 or more times. The disadvantage of this drying method is the need to have an adjustable non-standard voltage power supply. In this case, the connection schemes of the windings can be different. The drying temperature and its mode depend on the heat resistance class of the machine and the brand of impregnating varnish. The completion of drying can be judged by the established resistance of the insulation being dried (at a given constant temperature).
The most common method of impregnation is the immersion of a winding heated to 60 ... 70 ° C in a varnish of approximately the same temperature. The number of impregnations depends on the purpose of the machine, in agricultural production it is recommended to carry out up to three impregnations. The duration of impregnation is 15...30 minutes for the first and 12...15 minutes for the last.
After vacuum drying, pressure impregnation can be applied for critical machines. But to provide the first and second processes, relatively sophisticated equipment is required.

electromechanical work includes: repair of machine bodies, end shields, shafts, bearing assemblies, active iron of the stator or rotor, collectors, slip rings, brush devices and short-circuited mechanisms, poles, squirrel cages and output boxes. In addition, these works include shrouding of rotors and armatures and their balancing.
In the conditions of electrical repair enterprises of the State Committee for Agriculture, the iron of the stator and rotor, the poles and squirrel cages of the rotors are usually not repaired. Cars with such damage are considered non-repairable, they are not accepted for repair and are written off for scrap.
Repair of housings and end shields, as a rule, consists in the elimination of fractures and cracks and is carried out by welding.
Currently, almost all electrical machines have rolling bearings, maintenance and repair of which is much easier than plain bearings.
Rolling bearings are usually replaced when worn. If there are no bearings of the required standard sizes, bearings with other sizes can be used, but the new bearing must correspond in its load capacity to the replaced one. In this case, internal or external auxiliary (repair) bushings are used, the fit (coupling) of which is carried out by pressing (with interference), and auxiliary thrust rings are used under the outer ring of the bearing.
Roller bearings can be replaced with ball bearings in cases where significant axial forces are not observed during operation of the machine (the run-up of the mechanism shaft does not exceed the run-up of the electric motor).
Ball bearings have a tight fit on the shaft, therefore, before landing on the shaft, they are heated in an oil bath to a temperature of 80...90°C.
Collector repair can be carried out with or without disassembly. Repair without disassembly consists of turning (on a lathe or in our own bearings), chipping, grinding and polishing. The cutting of the collector (using a cutter on the machine, a hacksaw blade or a special scraper) is performed with each repair of the collector, even if it has not been grooved.
When repairing or replacing the insulation between the collector plates, one should strive not to disassemble the collector completely, but to use a detachable clamp, which significantly reduces the labor costs for disassembling and especially for assembling the collector. For low-voltage machines, new collars can be molded directly during assembly of the collector without the use of special molds.
The repaired, fully assembled manifold is heated in a furnace to a temperature of 150 ... 160 ° C, tested on a machine for mechanical strength at a frequency of rotation 1.5 times higher than the nominal one and checked for the absence of short circuits between the plates and between the plates and the bushing.
Slip rings are repaired if their thickness in the radial direction reaches 8 ... 10 mm (less than 50% of the original). The design of the assembly with slip rings can be very diverse: a split sleeve, insulation from electrical cardboard, flexible micanite and rings; solid sleeve, split sleeve made of sheet steel, insulation made of electric cardboard and rings; a continuous bushing with insulating figured rings, between which the machine rings are located; solid sleeve, mikafolium or micanite insulation and rings. All designs of slip ring assemblies, except for the last one, are assembled with an interference fit in a cold state.
The slip rings are checked for the absence of short circuits between them and the housing and runout (radial runout should not be more than 0.1 mm at a speed of up to 1000 rpm and 0.05 mm at a higher speed, and axial runout should not exceed 3 .., 5% of the ring thickness).
Repair of brush devices (traverse with fingers, brush holders with springs and clips and brushes) most often consists in restoring the insulation of the brush holder fingers, reliable contact between the bundles and the brush, adjusting the brush holder springs and installing, adjusting and running in the brushes. The brush holders are insulated with getinax end washers and bakedized paper on the neck of the finger with a thickness according to the repair process chart.
The choice of brushes depends on the purpose of the machine and the features of its operation. It is recommended to install electrographite brushes (EG) in exciters of an AC machine, allowing a current density of 9 ... 12 A / cm 2 and a linear speed of rotation of 40 ... 45 m / s; in crane engines - carbon-graphite (T and UG) with parameters of 6 A / cm 2 and 10 m / s and electrographite; in low-voltage generators (up to 20 V) - electrographite and copper-graphite (M and MG) with parameters 14 ... 20 A / cm 2 and 15 ... 25 m / s; in automobile electric machines - copper-graphite; in machines with slip rings - graphite (G), electrographite and copper-graphite.
The pressure of the brushes is recommended in the range from 1500 to 2000 Pa.
Repair of the short-circuit mechanism consists in restoring the worn side ribs of the short-circuit ring, fork pins and spring contacts by welding and surfacing, or replacing the worn part with a new one.
Stockings or keeper tape are used to bandage the stator windings of machines of relatively low power. The frontal parts of the windings of various coils and phases are fastened with a bandage into a single whole unit, which, after impregnation and drying, becomes monolithic. This provides the necessary mechanical strength of the winding during starts and sudden overloads of the machine. In large machines, so-called bandage rings are used, they are placed on top of the outer frontal parts of the machine coils. Each coil is tied with a keeper tape to the ring.
A special role is played by the shrouding of the windings of the rotors and armatures of machines, which experience not only electrodynamic loads during the operation of the machine, but also centrifugal forces. Rotors and anchors are shrouded on turning or special shrouding machines equipped with devices for tensioning tinned steel shrouding wire.
A layer of insulation made of micanite and electric cardboard is laid between the winding and the wire. With a wire diameter of 0.6 to 2 mm, the wire tension should be from 200 to 2000 N, the number of turns of the bandage is calculated for centrifugal forces, which should not exceed 400 N per 1 mm 2 wire section. The bandages are soldered around the entire circumference to turn them into a continuous ring.

In repair practice, parts from various materials are restored using manual arc and gas surfacing and welding, automatic surfacing and welding under a layer of flux, vibro-arc surfacing in a coolant jet, welding and surfacing in a shielding gas environment, electric spark processing and build-up both in air and in a liquid medium, metallization, ostalivaniya, chemical nickel plating.
When repairing electric motors, a relatively large amount of work is to increase the seating surfaces. For these purposes, vibro-arc surfacing with flux-cored wire and surfacing in a carbon dioxide environment are widely used. The first is used to restore shafts, axles and pins with a diameter of more than 30 mm. At the same time, the hardness of the surfacing layer is 1.5...2 times higher compared to the hardness of the layer obtained by vibro-arc surfacing in liquid. This improves the quality of the surfacing layer.
After surfacing, a groove is made and the surface is polished, and if necessary, grooves (spline grooves) are milled.
For finishing shaft surfaces instead of grinding, hardening the surface layer to a depth of 0.2 ... 0.3 mm, increasing wear resistance and fatigue strength of the part, an electromechanical processing method is used, which consists in the fact that when processing a part on a lathe, a part and a cutter a voltage of 2 ... 6 V is applied and a current of 350 ... 1500 A flows at the place of their contact.
Cast iron beds and bearing shields are welded with gas welding. Before surfacing, the parts are heated in a furnace to a temperature of 300 ... 400 ° C, while cast iron electrodes are used, borax or other mixtures are used as a flux.
After surfacing, the parts are fired at the same temperature for 4...6 hours, after which they are slowly cooled in the switched off furnace (12...14 hours). Recently, at the repair enterprises of the Goskomselkhoztechnika system to restore seats under the bearing in the housings of parts, installations for galvanic electron rubbing are used.
Restoration can be subjected to holes with a diameter of 50 to 150 mm. The principle of operation of the installations is based on the electrolysis process, accompanied by metal deposition on one of the electrodes. The part to be restored is connected to the negative pole of a power source with a voltage of 24 to 30 V, for example, a PSO-300 converter. An electrode wrapped in a material capable of absorbing (absorbing) electrolyte is inserted into the restored hole. The electrolyte is supplied to the absorbent material by means of a pump with a flow rate of 20 l/min. When the electrode rotates at a frequency of 20 to 40 rpm (using any vertical drilling machine) an electrolytic bath is created in the absorbent material, in which the electrolysis process takes place. A set of electrodes consists of steel parts wrapped with absorbent material, which can be used as cotton fabric, for example, keeper tape with a layer of up to 2.5 ... 3 mm. The gap between the absorbent layer and the surface of the growing hole is 1.5...2 mm.
To build up parts made of steel and cast iron, an electrolyte of the following composition is used: zinc sulfate - 600 ... 700 g per liter of warm water and boric acid- 20...40 g per liter of warm water. The acidity (concentration) of the electrolyte pH = 3...4, it is checked monthly, and once a month the electrolyte is completely replaced.
For aluminum parts, a solution of 150 g of aluminum sulfate in a liter of water is used as an electrolyte. The acidity of the electrolyte is pH=3...3.5.
The current density during etching, which precedes the growth, is 1 ... 1.5 A / cm 2 (etching duration 8 ... 10 s) and when growing 2 ... 3 A / cm 2. The growth rate is 20...30 µm/min.
Preparation of the bearing shield for restoration consists in cleaning it with fine sandpaper, degreasing with a rag soaked in gasoline or acetone, and drying. With the extension method described, it is necessary to insulate the table of the drilling machine in order to use the body and table as clamps of different polarity. For safety reasons, the electric motor is isolated from the machine body. The worker serving the installation works in glasses, a rubber apron and rubber gloves. The floor of the machine is lined with rubber mats. Installing and removing parts is only allowed when the power is off.
Recently, elastomers have been used to restore seats for bearings, in particular GEN-150 (V). To dissolve 20 parts by weight of elastomer, 100 parts by weight of acetone are needed. The part to be restored is cleaned of dirt, corrosion, degreased, cleaned with acetone and dried. The elastomer is applied to the part through a tube.

Tool used

In the process of maintenance and repair of a squirrel-cage induction motor, the following tool is used:

Alignment ruler

Staples and strings

Rulers with pulleys of different widths.

Wrenches 6 - 32 mm - 1 set.

Files - 1 set.

Set of heads - 1 set.

Metal brush - 1 pc.

Repair knife - 1 pc.

Screwdriver set - 1 set.

Locksmith's screwdriver - 1 pc.

Dies 4 - 16 mm - 1 set.

Taps 4 - 16 mm - 1 set.

A set of drills 3 - 16 mm - 1 set.

Mount - 1 pc.

Pliers - 1 pc.

Chisel - 1 pc.

Drill - 1 pc.

Core - 1 pc.

Flat brush - 2 pcs.

Hammer - 1 pc.

Shovel - 1 pc.

Basting brush - 1 pc.

Technological map of repair and maintenance of an asynchronous motor with a squirrel-cage rotor

Name and content of works	Equipment and fixtures	Technical requirements
External inspection of an electrical machine, including control, protection, ventilation and cooling systems.	Compliance with technical data sheets for operation and electrical diagrams.
Visual check of the condition of the grounding conductor; checking the condition of the ground loop.	Hammer, shovel	Lack of anti-corrosion coating, loose fastening, mechanical damage not allowed.
Check for the absence of extraneous noise.	Extraneous noise is not allowed.
Cleaning accessible parts from dirt and dust.	White spirit, rags, metal brush, sweeping brush.
Inspection of the connection elements of the engine with the driven mechanism.	Cracks at the seams, breaks, distortions, loosening of threaded connections are not allowed.
Checking the connection and reliability of the sealing of the incoming cables, technical condition and tightness of inlet boxes and sealed inlet couplings; checking the condition of seals, surfaces and parts providing explosion protection; explosion-proof cable and wire entries.	Set of locksmith's probes No. 1 Set of tools set of screwdrivers Set of heads.	The roughness of the working surface Rd is not more than 1.25 microns.
Checking the fastening of the electric drive to the frame (valve).	Set of tools. Set of heads.	Loose fasteners are not allowed.
Inspection of the state of start-up and control equipment (PRA).
Purging the stator and rotor with compressed air.	Compressor.
Checking the insulation resistance of the windings; drying if necessary.	Megger 500V.	The insulation resistance must not be less than 0.5 MΩ.
Checking the pairing of parts that ensure tightness.	Set of bench probes No. 1. A set of tools, a set of screwdrivers. Set of heads, sealant.	The clearances are specified in the instruction manual.
Checking the presence of lubrication in the bearings of the electric motor, (if there is a grease fitting, replenishment).	CIATIM grease - 221, syringe for pressing grease.

	Set of tools. Screwdriver Set.
	Brush, paint (tablet).
Inspection, cleaning and tightening of contact connections.	Set of tools. Grinding fabric skin according to GOST 5009-82.	Distortions, the presence of oxide, loosening of contact connections are not allowed.
Revision of automatic switch assemblies.	Set of tools. Screwdriver Set.
Checking the presence of cable markings, inscriptions and symbols on the casing, if necessary, restoration.	Brush, paint (tablet).	Lack of marking and inscriptions are not allowed.

Security measures

The electric motor must be de-energized, the AB is turned off, grounding is installed, posters are hung out. Apply portable grounding to the input ends of the electric motor cable. Secure the work site. Work with PPE. Work with trusted instruments and tested power tools and fixtures.

The composition of the brigade

An electrician for the repair of electrical equipment with an electrical safety group of at least the third. Electrician for the repair of electrical equipment with the third electrical safety group.